Red mud is an industrial solid waste discharged during the extraction of aluminum oxide in the aluminum industry. Its high alkali content limits its utilization. Using calcium carbide slag to replace natural calcium-based materials for red mud dealkalization, the effect of four factors including dealkalization’s temperature, carbide slag’s dosage, liquid-solid ratio and reaction time on red mud dealkalization were analyzed, and the reaction mechanism of calcium carbide slag for red mud dealkalization was explored. The results show that as the temperature increases, the amount of calcium carbide slag increases, the reaction time increases and the dealkalization efficiency increases. Under the reaction condition of temperature 90 ℃, liquid-solid ratio 4∶1, reaction time 6 h and a 1∶1 mass ratio of red mud to calcium carbide slag, the dealkalization efficiency reaches 81%. After dealkalization, the Na2O content in the red mud is not more than 1% (mass fraction), which meets the standard for use as cement raw material. For red mud dealkalization reaction by calcium carbide slag conforms to the internal diffusion unreacted shrinking core model, and increasing the reaction temperature or the amount of reactants can improve the dealkalization rate.